Method of carroting fur



Patented Nov. l, 1932 UNITED STATES PATENT oer-ice GEORGE D. IBEAL AND RUB BOY MCGBEGOR, OF PITTSBURGH, rinnrsxnvmm, 881G17- ORS TO MELLON INSTITUTE OI INDUSTRIAL RESEARCH, A CORPORATION 01 PIN!- SYLVANIA TRUSTEE No Drawing,

Our invention relates to the treatmentof animal fibers, such as fur, in preparation for its manufacture into felt. It has been developed in the treatment of fur, and in that [6 application we shall describe it. The objects in view are improvement in the quality of the product, reduction in the cost of production, and avoidance of manufacturing conditions such as to afi'ect'the health of o 10 eratives. The preponderant use for fur is t is in the making of hats.

For the preparation of fur for felt manufacture it has long been the practice to treat rabbit, hare, beaver, and slmilar types of fur with a solution of mercuric nitrat-ein nitric acid, either while still on the pelt or after removal therefrom. The fur is then dried at temperatures rangin from room temperature to as high as 250 depending upon the nature of the fur and the t pe of final product desired. The process is nown as carroting. a

There are certain disadvantages connected with the process, among which the most obvious are the toxicity of the mercury and the discoloration efiected by the nitric acid; also, varying results are obtained under varying atmospheric conditions, due to the fact that the nitric acid is volatile. This property of nitric acid results in a quick evaporation of the nitric acid on days of low relative humidity and slow evaporation on days of high relative humidity. On days of low relative humidity much of the nitric acid may evaporate before reacting with the fur, and on days a of high relative humidity the time of reaction of the acid with the fur may be so greatly prolonged as to give a decidedly yellow color to the fur, regardless of the temperature of drying.

it is evident that there is a need for a carroting solution which will do away' with the (lifliculties consequent upon the use both of mercury and of nitric acid.

\Ve have made an extensive study of the reactions of carroting solutions uponfur, and

have found that, in order to obtainthe best results, two reactions must take place. The first reaction is that of oxidation, and in the mcrcuricnitrate-nitric-acid solution this re- METHOD or cannormo run Application filed November 1, 1930. serial No. 494,101.

action is carried out b the mercury catalytically and by'the nitric acid by direct oxidation. The second reaction is that of hydrolysis of the fur, to allow the oxidizing agent to penetrate andto carry out its function more readily and com letely. In the solution in commonuse this function devolves on the nitric acid. But this acid is far from being consistent, due to the fact that part of it is expended in oxidation and nitration, and its time of contact with the fur varies according to the temperature of drying and accordin to the degree of humidity of the atmosp ere.

We have found as a result of many experiments that neither oxidation alone or hydrolysis alone is sufiicient to ive a good carroting effect. The use of hy rogen peroxide, or of potassium permanganate, or of similar oxidizing agents, does ive a certain carroting effect, but not near y sufiicient to be of commercial value. Hydrolysis by the use of sulphuric acid, or of hydrochloric acid, or of steam under pressure, also achieves a certain carroting effect, but not sufiicient to be of commercial value. The combination of these two reactions, however, brings about a carrotin reaction which is com lete and which a lo ing worked faster and of better qualit than fur treated with mercury solution. T e improvement of our process u on the mercury solution process is, without oubt, due to our use of a proper h drolyzing agent.

We have foun that the best results are obtained by the use of an oxidizing a ent which is readily available, accompanie by a hydrolyzing acid which isnot volatile at the temperature at which the carroted fur is dried, and which is not consumed by the fur substance through oxidation reactions on the part of these acids at temperatures not exceeding the temperatures at which the fur is dried.

As oxidizing agent we use hydrogen peroxide. As hydro yzing agent we may use such acids as sulphuric, or phosphoric, or any highly ionized acid which is not volatile at the temperature of drying and which may not be consumed by side reactions during the rds a carroted fur capa le of beprocessing. We prefer to use sulphuric acid.

We recognize the fact that hydrogen peroxide alone has been proposed as a carrot- I ing solution, also hydrogen peroxide with catalysts to (promote the oxidizing effects, as well as by rogen peroxide with alkalies. None of these gives the complete efi'ect desired. Hydrogen peroxide alone is not nearly active enough for the purpose; the addition of catal sts assists the oxidation, but from our stu ies we believe that the lack of a hydrolytic a cut is a serious detriment. The addition 0 an alkali has undoubtedly a h drolytic efiect, but its action is too harsh. oreover, it is frequently found that furs which have been carroted with alkalies (with or without hydrogen peroxide) must be felted down in a more or less continuous operation. Allowing the partiall felted material to stand overnlght frequent y robs it of the ability to felt further. We believe that an explanation for this is to be found in the fact that the isoelectric point of fur is in the neighborhood of a pH of 5. The alkaline carrot is so far removed from this that probably an unusual amount of swelling of the fiber takes place, resulting in a harshness and a weakening of the fiber. Further than this, the hydrolytic effect of alkalies upon probeins is much more vigorous than that of, acids and is, consequently, more .difiicult of control. The acid carrot, havin a pH closer to that of the isoelectric point 0 the fur than an alkaline carrot causes less swelling and therefore avoids the development of harshness, while the gentler hydrolytic efi'ect is much more susceptible to control.

Whether this be the true explanation or not, we have demonstrated that fur prepared with an acid as the hydrolytic agent has the advantage of producing a finer feeling felt and also of allowing felting to be completed in other than a continuous operation.

As an example of our method, we prepare a 10% solution of hydrogen peroxide '(by dilution of the commercial 30% product) and add to this an equal volume of Q-normal sulphuric acid. The solution is then ready to be applied to the fur.

After the fur has been treated it is dried, the fur removed from the elt, and it is then ready for the operations of blowing and hatmaking. The fur so prepared has been found to work as well as mercury-carroted fur, and in the practice of our invention we have found that it is possible to maintain more nearly the natural color of the fur than in the practice of the mercury-carroting process.

The concentration of hydrogen peroxide and sulphuric acid may vary wldely, according to the nature of the fur being treated and to the method of drying. The percentage of hydrogen peroxide in the final solution may var from 2% to 10% and of the sulphuric aci from 0.3 normal to 1.5 normal.

Different types of fur and different types of dryin call for different concentrations both of hy rogen peroxide and of sul huric acid; and, within the limits named, the est proportions may be found only by test.

Inasmuch as hydrogen peroxide may be produced by the decomposition of certain per salts of alkalies and alkaline-earth metals such as perborates and percarbonates and by the decomposition of-alkalies and alkalineearth peroxides with acids, we may choose to use such salts and peroxides together with sulfuric acid to produce the same effect upon the fur. We may also choose to use organic peroxides as the oxidizing agent together with our non-volatile acid.

We claim as our invention:

The method herein described of simultaneously hydrolyzing and oxidizing fur fiber in preparation for felting which consists in treating the fiber with a solution containing hydrogen peroxide in concentration ranging from 2 to 10 per cent. and sulphuric acid in concentration ranging from 0.3 normal to 1.5 normal.

In testimony whereof we have hereunto set our hands.

GEORGE D. BEAL. ROB ROY MoGREGOR. 

